German Patent No. 39 20 080 described an ignition system for an internal combustion engine in which a spark plug is inserted into a spark-plug compartment (well) of a cylinder head of the internal combustion engine.
A cylinder-head cover is placed on the cylinder head, with the interposition of a gasket. Above the spark-plug compartment, the cylinder-head cover has an installation opening into which is inserted an ignition coil that is connected to the spark plug by way of a connecting plug.
If spray water, e.g. from a high-pressure cleaner, acts upon the ignition coil, this water can get through the installation gap into the installation opening, and from there into the spark-plug compartment. This can occur in particular when the cylinder head is heated to above 100.degree. C. due to the operation of the internal combustion engine, and, during the standstill phase of the internal combustion engine, is cooled off to the ambient temperature. In so doing, the air volume in the spark-plug compartment and the installation opening contracts; an underpressure develops which evens out due to advancing air and moisture along the contact area of the ignition coil. The moisture thus introduced forms a liquid pool around the spark plug, and can impair the high-voltage transmission of the ignition coil, which can result in malfunctions of the ignition system.